Developing device for a polychromatic electrophotographic copier

ABSTRACT

A developing device which can obtain a blend free polychromatic development in the same position. The device successively makes an electrostatic latent image visible using polychromatic developer and comprises developer supply means, developer holding means having an endless holding member, and developer recoverying means, whereby developer once used may be recovered for reuse.

United States Patent [19] [none et a1.

[4 1 Oct. 7, 1975 [73] Assignee: Canon Kabushiki Kaisha, Tokyo,

Japan 22 Filed: Feb.19, 1974 21 Appl. No.1 443,260

[30] Foreign Application Priority Data Feb. 21, 1973 Japan 48-21090 [52] US. Cl. 118/637; 117/37 LE; 118/D1G. 23; 355/4 [51] Int. Cl. G03G-15/10 [58] Field of Search 355/4; 117/37 LE; 118/D1G. 23, 602, 637; 96/12 [56] References Cited UNITED STATES PATENTS 2,590,538 3/1952 Huck 118/602 2,649,758 8/1953 Cowgill 1 18/602 3,663,100 5/1972 ltoh et a1. 355/4 3,669,073 6/1972 Savit et a1. 117/37 LE 3,687,107 8/1972 Borelli et a1. 118/637 3,701,337 10/1972 Borelli et a1. 118/637 3,705,767 12/1972 Tamai et a1 355/4 3,766,887 10/1973 Sato et a1 118/D1G. 23

3,779,639 12/1973 Tamai 355/4 3,789,794 2/1974 Smith et a1 118/602 3,809,557 5/1974 Pressman et a1 355/4 Primary ExaminerMervin Stein Assistant Examiner-Douglas Salser Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper & Scinto [5 7 ABSTRACT A developing device which can obtain a blend free polychromatic development in the same position. The device successively makes an electrostatic latent image visible using polychromatic developer and comprises developer supply means, developer holding means having an endless holding member, and developer recoverying means, whereby developer once used may be recovered for reuse.

10 Claims, 13 Drawing Figures Sheet 1 of 6 U8. Patent Oct. 7,1975

Sheet 2 of 6 3,910,231

US. Patent Oct. 7,1975

US Patent 0a. 7,1975 Sheet 3 of 6 3,910,231

I M32 M83 5 M84 VVV iii ++1 U.S. Patent 0a. 7,1975 Sheet4 0f6 3,910,231

U.S. Patent 0a. 7,1975 Sheet5 of6 3,910,231

FIG. '8

US. Patent Oct. 7,1975 Sheet 6 of6 3,910,231

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for a polychromatic electrophotographic copier, and more particularly to a compact developing device which can obtain a color image of good quality by successive development using various developers in one developing device.

2. Description of the Prior Art In color representation methods for a polychromatic electrophotographic copier conventionally employed, there is a direct system which forms a polychromatic image using various developers placed one above the other on the same photosensitive body, and a transfer system which forms a polychromatic image by forming the image color after color onto the photosensitive body, said image being placed one above the other on transfer paper and the like. These systems however give rise to trouble when they are applied to the developing device. That is, in the direct system, the developer is successively placed on the photosensitive body one above the other, and consequently developer other than needed may possibly'mingle into the developing device even if an image previously developed is fixed prior to performing the succeeding development, and therefore a specified color is often hard to be represented satisfactorily. In addition, since the colors are likely to be blended in each developing device, it is greatly affected by the blend of developer, thus lowering the copying efficiency. To prevent such drawback, developing devices according to the colors may be provided in spaced relationship so that they are moved to the developing station each time for development. However, the above-described construction complicates the developing device and the moving mechanism of the developing device and in addition the copierin itself becomes large in size. This arrangement further has such disadvantages that due to movement of the developing device, developer is scattered and dropped, and then flows to the moving parts of the developing device and adheres thereto, thus interfering with the moving mechanism. In the transfer system, there are such disadvantages that if polychromatic developing devices are aligned in the developing station so as to successively effect one-color development every copying cycle, the developing station would occupy more, and the time required from formation of a latent image to development and from development to transfer are different depending on the developing device for each color, and consequently all of the colors can not be de veloped under the best conditions, thus resulting in a poor color representation.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a developing device which can provide a blend free polychromatic development in the same position.

It is another object of the invention to provide a highly efficient developing device which can recover and reuse the developer once used.

It is a further object of the invention to provide a developing device which can provide development of good quality without producing fog.

It is yet another object of the invention to provide a developing device of a compact construction.

In brief, the present invention relates to a developing device using polychromatic developer for successively making visible electrostatic latent images formed on an image carrier, such device comprising developer supply means for supplying developer of a predetermined color to said image carrier, developer holding means having an endless holding member for holding and moving developer supplied from said developer supply means, and developer recovering means for recovering developer, held and moved by said developer holding means, after every predetermined color development.

BRIEF DESCRIPTION OF THE DRAWING The drawings illustrate a polychromatic developing device, wherein:

FIG. 1 is a side view illustrating the device constructed in an endless-belt like manner;

FIG. 2 is a perspective view showing a modified form of the device;

FIG. 3 illustrates a device constructed in a drum-like manner in which a developer supply system is diagramatically illustrated;

FIG. 4A illustrates a change-over mechanism for recovering developer;

FIG. 4B is an electrical control circuit associated with the mechanism of FIG. 4A;

FIG. 5 illustrates a specific embodiment of a developer supply station;

FIG. 6 illustrates a developing electrode;

FIG. 7 illustrates a further embodiment in modified form;

FIGS. 8 and 9 illustrate a device applied to the beltlike photosensitive body;

FIG. 10 illustrates a device applied to a plate-like photosensitive body; and

FIGS. 11 and 12 illustrate a further embodiment in modified from.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a basic construction of the device according to the present invention is shown. On a drum is mounted a photosensitive body for holding an electrostatic latent image formed in accordance with a known electrophotographic process or a latent image carrier 1 such as a transfer material having the electrostatic latent image transferred and held thereon, which is rotated in a direction as indicated by the arrow. Developer D for making said latent image visible is injected and supplied from a supply pipe 4 through a developer supply inlet 3. This developer D flows down on a developer holding endless belt 6 which is held and rotated by an endless belt drive shaft 7 and rotary shafts 8 and 8'. This developer holding endless belt 6 is made of a conductive materials such as metal, conductive rubber, conductive resin and the like and is insulated from the body of the device so that a bias voltage may be applied in order to further improve the developing effect at the developing station where the belt 6 is in engagement with the image carrier 1 such as photosen sitive body when the developer flows in. That is to say, if the bias voltage has the same polarity as that of developer, an electrostatic repelling power acts between the developing electrode and the developer whereby the developer is easily attracted by the photosensitive body to enhance the developing effect. On the other hand, if the bias voltage has its polarity different from that of the developer, an electrostatic attraction occurs to attain the effect for removing fog from the photosensitive body where an image is not formed, and a construction for effectively carrying out said effect will be later described. Further, if endless convex parts 6a are provided on the opposite ends of the developer holding endless belt 6 as shown in FIG. 2, it will have the effect such that when developer flows between the photosensitive drum 1 and the developer holding endless belt 6, the developer is prevented from flowing down sideward. Also, the convex parts 6a may be arranged in contact with the photosensitive body so as to drive the endless belt in the direction indicated by the arrow 2. These convex parts are useful to maintain the photosensitive body and the endless belt at a predetermined spacing so that the developer flows uniformly on the developer holding endless belt 6 and a surface of the same height as said flow surface is placed in contact with the photosensitive body, thus providing for a uniform development. Especially; a better development effect may be attained by setting a clearance between the photosensitive body and the holding belt to a distance from 0.2 to 2.0 mm. In the case where speed of the photosensitive drum 1 is different from speed of the developer holding endless belt 6, developer is wellstirred at a portion where the photosensitive drum 1 is brought in contact with the developer holding endless belt 6, and accordingly it will have the effect of effecting development with developer of a constant high concentration without being deposited. The developer holding endless belt 6 is pressed by means of a pressing roller 9 to take up slack between rotating shafts 8, and 8 so that flatness of the developer holding endless belt 6 may be ensured and so that a clearance between the photosensitive drum 1 and the developer holding endless belt 6 is made constant, to produce the effect of forming an image of uniform concentration. The developer holding endless belt 6 passes through the developing station then passes a developer recovering station. In this recovering station, there is arranged a predetermined number of units including a developer recovering blade 10 secured to a rotatable blade shaft 1 l and the units including developer recovering blades are disposed for operation in response to each color representation.

For example, arrangement is made such that in the case where a first color has been developed, only the developer recovering blade 10 for the first color is operated and placed in contact with the developer holding endless belt 6 with developer recovering blades 10 10 10 etc., for a second color, a third color, and a fourth color, remaining, inoperative without being placed in contact with the developer holding endless belt 6. The developer recovered by the developer recovering blade 10, in the manner as described is then introduced into a developer recovering tank. Thereafter, the developer is introduced through a pipe 21 from the developer recovering tank 12 to a developer supply tank 22 for the first color with the aid of a pump. In this developer recovering station, an endless belt pressing plate 19 is provided on the opposite side of the belt 6 from the developer recovering blade so as to prevent the developer holding endless belt 6 from being slackened when in contact with the blade. Accordingly, the developer may be efficiently recovered by thefdeveloper recovering blade into developer recovering tanks l2 12 12 and l2 Developer recovered into the developer recovering tanks 12 12 12 and 12 is introduced to developer supply tanks 22,, 22 22 and 22 and if necessary, developing agent is added therein to again form them into a constant concentration for use as developers.

In FIG. 3, there is shown an embodiment ofa circulation system for the aforesaid developer supply and recovery.

in FIG. 4A, illustrating a change-over mechanism of the developer recovering blade, there is provided a cam plate which rotates once for every four revolutions of the photosensitive drum 1, said cam plate being provided with cams CM,, CM which control the opening and closing of a predetermined number of microswitches M8 M8 These micro-switches M3,, M5 opened and closed by the cams CM CM activate solenoids SL SL adapted to rotate developer recovering blade shafts ll, 11'

FIG. 48 illustrates an embodiment of an electrical control circuit associated with the mechanism of FIG. 4A.

After the developer has been recovered by the developer recovering station as previously described, the developer holding endless belt 6 passes at a washing station having a washing liquid guide plate 15 to guide washing liquid flowing from a supply pipe 14 so as to bring liquid onto a washing brush 13, which is always rotating for cleaning the developer holding endless belt 6 to place it in condition for the succeeding color development. The washing liquid after use is recovered into a washing liquid recovering tank 16. The washing liquid thus recovered is discharged through a washing liquid discharging pipe 17, and if necessary, the recovered washing liquid is introduced into a filter 23, where said liquid is filtered and cleaned, and then recovered by a washing liquid supply tank 24. Then, liquid is again lifted from the washing liquid supply tank with the aid of a pump, etc. for use as a washing liquid.

The developer holding endless belt 6 thus washed is returned to the developing station. FIG. 5 illustrates a developer supply station. In the developer supply inlet 3, developer supply openings for each color are aligned in order, each opening being connected by distribution pipes 3 3 3 and 3 respectively, branched from developer supply pipes 4 4 4 and 4 respectively, for each color. These supply pipes 4 4 4 and 4 are in turn connected to developer tanks 22 22 22 and 22., for each color. Developer supply pipes 4 4 4 and 4 are provided with developer control valves 5 5 5 and 5 respectively. In the case where the first color development is carried out, only the developer control valve 5 for the first color is opened with the developer control valves 5 5 and 5 for the second, third, and fourth color, respectively, remaining closed. The same is true for the succeeding development. It is to be understood that this control mechanism may be used in cooperation with the mechanism as illustrated in FIGS. 4A and 4B, or if necessary it may be provided independently.

As discussed in the foregoing, according to the developing device of the present invention, development is made by developer supplied from the developer supply inlet 3 for the first color, whereupon developer remain ing on the developer holding endless belt 6 is recovered by the developer recovering blade 10 for the first color while the developer holding endless belt 6 is washed.

developer supply pipe 4 for the second color, whereupon developer remaining on the developer holding endless belt 6 is recovered by the developer recovering blade 10 for the second color while the developer holding endless belt 6 is washed clean by the washing brush 13 in the washing station. Then, developer for the third color and developer for the fourth color are successively provided from the developer supply pipes 4 and 4 for the third and fourth colors, respectively, and polychromatic development is completed in a cycle similar to the aforesaid manner.

Although the process of polychromatic development has been described in the manner in which develop ment is repeated one color after the other, it should be understood that the second color development may be accomplished at the stage where liquid is being recovered after termination of the first color development, is not limited to such successive development as described above.

Specific embodiments of the present invention will be described further with reference to the accompanying drawings. 7

In the embodiment shown in FIG. 1, thereis employed a developer holding endless belt held in triangular configuration, while in FIG. 3 there is employed a drum-like configuration. In the illustrated construction of FIG. 3, the photosensitive body is placed in linear contact with the developer holding drum 61 so as to attain the effect of removing fog therefrom. Thus, a bias voltage opposite in polarity to that of developer is applied to the drumby a power supplyPS. On the other hand, the developing effect provides a sufficient image representation through the ejectionsupply from .the developer supply station and a developing electrode stationarily mounted. This developing electrode is applied with a bias voltage of the same polarity as that of developer. In this way, developer ejected and supplied from the developer supply pipe 3 is introduced into the de veloping station, where development is carried out, whereupon developer remaining on the developer holding drum 61 is recovered by the developer recovering blade 10 into the developer recovering tank- 12 and the developer holding drum 61 is washed clean by the washing brush 13, and then developer for the second color flows out of the developer supply pipe for thesecond color for the repetition of a cycle similar to the above, and development is carried out by placing one color above the other to form a polychromatioimage,

Also, in a case where the developer electrode of the above-described construction is utilized, a better developing effect may be attained by the provision of a clearance from 0.2 to 2.0 mm between the developing electrode 27, as shown in FIGS. 6, 7, 8, l1, and 12, and the photosensitive-body 1. In the polychromatic development according to the present invention, it isinecessa'r y to successively feed developers of different colorswith out blending, Accordingly, if said clearance is made greater, a larger quantity of developer .rnust be fed. In addition, developer does not flow down uniformly onto the developing electrode 27, thus lowering the developing effect. If-said clearanceismade smaller, the devel-v oping effect may be improved, but it is attended by various disadvantages such that the position of the developing electrode'27. is difficult to maintain or the photosensitive body 1 may be damaged if foreign substance is mingled into developer, and therefore it may be proper to determine a clearance to the extent as described above. However, different from those construction shown in FIG. 1 in which the developing station also serves as a developer holding belt which always rotates, the construction according to the present embodiment employs the developing electrode 27 which is not moved, and therefore it is difficult to flow down developer on the electrode 27 after completion of developing process through such a small clearance as described above, thus leaving the possibility that developer may adhere to and remain on the developing station.

In order to remove such a drawback, a cam 30 is rotated clockwise by means of a spring 31 during the developing process, as shown in FIG. 6, and the developing electrode 27 is rotated and moved upward on the shaft 29 through a movable side plate 29 to maintain said clearance. An arrangement may be added so that when development is stopped for the period of time between the termination of development with respect to a certain color of developer and the beginning of development of the next color, solenoid 32 is'energized to effect a synchronous vertical movement so that cam 30 is rotated counterclockwise through a plunger 33 and a pin 33 disposed integrally therewith to rotate and move down; the electrode 27 so as to widen the clearance between the electrode 27 and the photosensitive body 1.

FIG. 7 illustrates an endless belt configuration in which the moving direction of the belt 62 is made opposite the moving direction of the photosensitive body FIG. 1 1 illustrates an embodiment wherein'instead of applying a bias voltage to the belt 62, said belt 62 is rotated in the same direction as that of the photosensitive body-1 and a reducing roller 34 with a bias voltage applied thereto is'disposed onthe side separated from the photosensitive body 1.

The reducing-roller 34 is made of a conductive member such as metal, conductive rubber, conductive resin and the like and is rotated in a direction reverse to that of the photosensitive body to function to adhere the excessive developer onto the belt 62 and at the same time to improve the developing effect.

FIG. 12 illustrates an embodiment wherein'the reducing roller 34, similar to that shown in FIG. 11, is arranged between the photosensitive body 1 and the belt 62 to be located adjacent the photosensitive body 1 and in contact with the belt 62. In this embodiment, developer adhered to the reducing roller 34 is wiped off by the belt 62 and is well recovered without flowing to other places, and the reducing roller is placed in contact with the photosensitive body always keeping its clean condition.

FIGS..8 and 9 illustrate an embodiment in which the present invention is applied to the developing device for a copier of the type in which .a flexible photosensitive body 1 is rotated-belt-like. In this case also, a modification of the reducing roller as shown in FIGS. 2 and 3 may be considered.

. FIG. 10 schematically illustrates an embodiment in which'the developing device according to the present invention is applied to a copier using a flat plate photosensitive body. In the illustrated embodiment of FIG.

10, there is employed a roller-like developing electrode 27.

As is apparent from the foregoing, in accordance with the device of the present invention, polychromatic developers may be changed-over and supplied in the same developing station, and said used developer may be recovered and washed so that a better development may always be obtained. Moreover, since such an arrangement is employed in which a developing voltage a fog removing voltage, or the like may be applied when necessary, an image representation of extremely high efficiency and good quality may be obtained. Furthermore, as can be understood from the foregoing embodiments, a compact construction may be obtained.

We claim:

1. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on an image carrier, comprising:

developer supply means for successively supplying different color developers to the image carrier;

- developer holding means including a rotatable endless belt for holding and moving said supplied developer away from said image carrier; and

developer collecting means including a collecting blade for contacting said endless belt to remove said supplied developer therefrom, and planar sup port means disposed on the side of said belt opposed to said collecting blade for maintaining contact between said blade and said belt.

2. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on an image carrier, comprising:

developer supply means including a supply inlet for successively supplying charged different color developers to the image carrier; developer holding means including a conductive guiding member for guiding said developer from said supply inlet into contact with said image carrier, and a rotatable conductive holding member having an endless surface for holding and moving said supplied developer away from said image carrier; means for applying a first voltage to said conductive guiding member, and means for applying a second voltage to said conductive holding member, wherein said first and second voltages are of opposite polarities, and said first voltage has the same polarity as said charge on said developers; and

developer collecting means for separately collecting said different color developers held on said holding member. 3. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on a movable image carrier, comprising:

developer supply means for successively supplying different color developers to the image carrier;

developer holding means including a conductive rotatable endless belt for holding and moving said supplied developer away from said image carrier;

developer regulating means including a conductive roller disposed adjacent said endless belt and said image carrier at a position downstream of said belt in the direction of movement of said image carrier; and

developer collecting means for separately collecting said different color developers held on said belt. 4. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on a movable image carrier, comprising:

developer supply means for successively supplying different color developers to the image carrier;

developer holding means including a conductive rotatable endless member for holding and moving said supplied developer away from said image carrier;

developer regulating means including an electrically biased member disposed adjacent said holding member at a position downstream of said holding member in the direction of movement of said image carrier; and

developer collecting means for separately collecting said different color developers held on said holding member.

5. A polychromatic developing device as set forth in claim 4, wherein said electrically biased member comprises a conductive roller facing said image carrier.

6. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on an image carrier, comprising:

developer supply means including a supply inlet for successively supplying different color developers to the image carrier;

developer holding means including a guiding member for guiding said developer from said supply inlet into contact with said image carrier, and a rotatable holding member having an endless surface for holding and moving said supplied developer away from said image carrier; and

developer collecting means including a plurality of collecting units for separately collecting said differ-. ent color developers held on said holding member.

7. A polychromatic developing device as set forth in claim 6, wherein said guiding member is pivotally mounted for movement to permit residual developer to flow rapidly to said holding member subsequent to the supply of each different color developer.

8. A polychromatic developing device as set forth in claim 6, further comprising means for applying voltages to said holding member and guiding member.

9. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on an image carrier, comprising: i developer supply means for successively supplying different color developers to the image carrier;

developer holding means including a rotatable endless member for holding and moving said supplied developer away from said image carrier; and

developer collecting means for separately collecting said different color developers held on said holding member, said collecting means including a plurality of movably mounted collecting blades, means for successively moving said blades into contact with said endless member to remove developer therefrom, and a plurality of developer receptables for receiving said different color developers removed by said blades.

10. A polychromatic developing device as set forth in claim 9, wherein said endless member is conductive, and further comprising means for moving said image carrier, and developer regulating means including an electrically biased member disposed adjacent said holding member at a position downstream of said holding member in the direction of movement of said image UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,910 ,231 Dated October 7, 1975 Inventor(s) ZO Inoue et a1.

It is certified that error appears in the above-identified patent and that said'Letters Patent are hereby corrected as shown below:

In the drawings, delete Figures 6-12.

Column 2, delete lines 31-39, referring to Figures 6-12.

Column 4, line 11, delete "in" and insert In Column 5 line 21 after "development," insert and Column 5 lines 53-67, Column 6, lines l-67, and Column 7,

lines l-2, should be deleted.

Claim 1 line 8, delete "and moving".

Claim 1, line 9, before "away" insert in contact with said image carrier and for moving excess developer Delete Claims 2 3, 4, 5 6, 7, 8 and 10 On the cover page "10 Claims" should read 2 Claims Signed and Scaled this twenty-third D3) of August 1977 [SEAL] Altest.

RUTH MASON C. MARSHALL DANN Aflesling ff Commissioner of Patents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,910,231 Dated October 7, 1975 Inventor(s) Shozo 1110116 12 8.1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the drawings, delete Figures 6-12.

Column 2, delete lines 31-39, referring to Figures 6-12.

. Column 4, line 11, delete "in" and insert In Column 5, line 21, after "development," insert and Column 5, lines 53-67, Column 6, lines l-67, and Column 7,

lines l-2, should be deleted.

Claim 1, line 8, delete "and moving".

Claim 1, line 9, before "away" insert in contact with said Q image carrier and for moving excess developer Delete Claims 2, 3, 4, 5, 6, 7, 8 and 10. On the cover page "l0 Claims" should read 2 Claims g Signed and Sealed this IwenIy-third D 3) of A ugus! 197 7 [SEAL] AlleSl.

RUTH C. MASON C. MARSHALL DANN Arres ing Off Commissioner of Patents and Trademarks 

1. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on an image carrier, comprising: developer supply means for successively supplying different color developers to the image carrier; developer holding means including a rotatable endless belt for holding and moving said supplied developer away from said image carrier; and developer collecting means including a collecting blade for contacting said endless belt to remove said supplied developer therefrom, and planar support means disposed on the side of said belt opposed to said collecting blade for maintaining contact between said blade and said belt.
 2. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on an image carrier, comprising: developer supply means including a supply inlet for successively supplying charged different color developers to the image carrier; developer holding means including a conductive guiding member for guiding said developer from said supply inlet into contact with said image carrier, and a rotatable conductive holding member having an endless surfAce for holding and moving said supplied developer away from said image carrier; means for applying a first voltage to said conductive guiding member, and means for applying a second voltage to said conductive holding member, wherein said first and second voltages are of opposite polarities, and said first voltage has the same polarity as said charge on said developers; and developer collecting means for separately collecting said different color developers held on said holding member.
 3. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on a movable image carrier, comprising: developer supply means for successively supplying different color developers to the image carrier; developer holding means including a conductive rotatable endless belt for holding and moving said supplied developer away from said image carrier; developer regulating means including a conductive roller disposed adjacent said endless belt and said image carrier at a position downstream of said belt in the direction of movement of said image carrier; and developer collecting means for separately collecting said different color developers held on said belt.
 4. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on a movable image carrier, comprising: developer supply means for successively supplying different color developers to the image carrier; developer holding means including a conductive rotatable endless member for holding and moving said supplied developer away from said image carrier; developer regulating means including an electrically biased member disposed adjacent said holding member at a position downstream of said holding member in the direction of movement of said image carrier; and developer collecting means for separately collecting said different color developers held on said holding member.
 5. A polychromatic developing device as set forth in claim 4, wherein said electrically biased member comprises a conductive roller facing said image carrier.
 6. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on an image carrier, comprising: developer supply means including a supply inlet for successively supplying different color developers to the image carrier; developer holding means including a guiding member for guiding said developer from said supply inlet into contact with said image carrier, and a rotatable holding member having an endless surface for holding and moving said supplied developer away from said image carrier; and developer collecting means including a plurality of collecting units for separately collecting said different color developers held on said holding member.
 7. A polychromatic developing device as set forth in claim 6, wherein said guiding member is pivotally mounted for movement to permit residual developer to flow rapidly to said holding member subsequent to the supply of each different color developer.
 8. A polychromatic developing device as set forth in claim 6, further comprising means for applying voltages to said holding member and guiding member.
 9. A polychromatic developing device, using a plurality of different color developers for successively developing electrostatic latent images on an image carrier, comprising: developer supply means for successively supplying different color developers to the image carrier; developer holding means including a rotatable endless member for holding and moving said supplied developer away from said image carrier; and developer collecting means for separately collecting said different color developers held on said holding member, said collecting means including a plurality of movably mounted collecting blades, means for successively moving said blades into cOntact with said endless member to remove developer therefrom, and a plurality of developer receptables for receiving said different color developers removed by said blades.
 10. A polychromatic developing device as set forth in claim 9, wherein said endless member is conductive, and further comprising means for moving said image carrier, and developer regulating means including an electrically biased member disposed adjacent said holding member at a position downstream of said holding member in the direction of movement of said image carrier. 